The proposed research is designed to study the role of androgen in aggressive behavior of mice. Four general problem areas will be considered. First, is the aggressive behavior of non-perinatally androgenized females exposed to testosterone in adulthood identical to that of perinatally androgenized females and to that of normal males? This will be assessed by carefully observing the fighting behavior of the test animals toward olfactory bulbectomized males. Second, can non-perinatally androgenized females be induced to fight in adulthood by exposing them to a "normal" mode of testosterone release? This will be considered by transplanting testicular tissue into females. Third, what role does perinatal androgen play in testosterone-induced aggression? Animals will be administered dihydrotestosterone as well as various dosages of testosterone propionate in infancy. And fourth, are animals exposed to androgen prenatally more responsive to testosterone in adulthood than nonprenatally exposed animals? This question will be considered by administering testosterone propionate prenatally to females and by administering cyproterone acetate to prenatal males. The proximity of females to males in utero also will be considered.